Kurtosis - PowerPoint PPT Presentation

Kurtosis. Karl L. Wuensch Department of Psychology East Carolina University. What is Kurtosis?. It is the extent to which scores are dispersed away from the shoulders of a distribution The shoulders are the points where Z 2 = 1, that is, Z =  1.

Copyright Complaint Adult Content Flag as Inappropriate

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation

Kurtosis

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

All of the scores are at the shoulders, none in the middle or the tails. This is a two-point binomial distribution, p = .5. I have superimposed a normal distribution so you can see where the shoulders are on a normal distribution.

The scores in this distribution are even further away from its shoulders. One could call this a “fat-tailed” distribution – it has an unusually large proportion of its scores way out in the tails.

You will be working with Student’s t distribution. It has kurtosis greater than that of a normal distribution, especially when its df are low. In the plot to the left, the dotted line is for the normal distribution. Notice that the t distributions have fat tails. Remember this when we start talking about the critical values for the t distribution.